Apparatus for controlling electric motors.



H. pm. APPARATUS FOR CONTROLLING ELECTRIC MOTORS.

APPLIOATIOI FILED KAY 21, 1909.

Patented Dec. 7, 1909.

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UNITED STATES PATENT OFFICE. I

HARRY E. DEY, 0F JERSEY CITY, NEW JERSEY, ASSIGNOR T0 BENT. CABLE, OFNEW YORK, N. Y.

Specification of Letters Patent.

Patented Dec. '7, 1909.

Application fled. May 21, 1909. Serial No. 497,423.

To all whom it may concern:

Be it known that I, HARRY E. DEY, acitizen of the United States, and aresident of Jersey City, in the county of Hudson and State of NewJersey, have invented certain new and useful Improvements in Apparatusfor Controlling Electric Motors, of which the following is aspecification.

My invention relates to that class of apparatus in which the speed ofthe load is controlled by a difierential electrical efiect on twomotors. Each motor is essentially composed of the usual elements knownas an armature and a field. Current is supplied to these motors and thefield magnets and is usually drawn from main line wires. That portion ofthe current which energizes the field magnets passes through resistancesor rheostats by means of which the field strength of one motor is variedrelative to that of the other. When the field magnets of the two motorsare so energized as to be of aboutthe same strength the load remainsstationary. When they are of different strengths the load will receivemotion determined by the difference between the motions of the 'twomotors. That this motion, received by the load, will be in one directionor the other according to which of the motors hasthe greater speed atthe time, necessarily follows. Assuming each motor circuit to receivethe same strength of current from the main line wire or other source ofenergy, variations in the strength of the field-magnets areproduced bycutting in or cutting out'resistance from their circuits. Theretherelative strength of the field magnets of the two circuits can be variedat will by so moving the armof the rheostat as to interpose greaterresistance in one circuit than the other proportionate to the differencein strength desired. This may be done by different rheostats for the twocircuits but I prefer to employ a single rheostat, serving as a primaryresistance for controlling both circuits as -more convenient, because inthis way, a single motion of the arm ofthe rheostat will cut into onecircuit the same amount of resistance which it cuts out of the other.

' When controlling a load at a distance where it is not practicable toobserve the amount of motion of load, for examgle, the

rudder of a ship controlled from the ridge,

it has been found desirable to move the indicator located at thecontrolling station to the shaft.

. with the worm wheel S of the desired position of the rudder, and havethe rudder move to that-position and automatically stop. To accomplishthis in the simplest way I provide in addition to the controllingrheostata second rheostat mechanically operated by the load andconnected in series with the magnets and the controlling rheostat. Asthe second rheostat is moved by the load it adds resistance to the lowresistance side and cuts out resistance from the high resistancecircuits and thus when it arrives at the predetermined osition the twocircuits become balanced an the load comes to a standstill. Thisprinciple of using a primary resistance to vary and control the relativestrength of the field magnets of two dynamo electric machines, and acounter resistance operated with the load to restore the balance of thecircuits may be appliedto various forms and uses of dynamo electricmachines.

In the accompanying drawing I have shown my invention as applied to twosimple motors rotating in opposite directions and working upon the loadshaft through a differential gear. 1

A, B, are the motors mounted upon the shafts a, Z), respectively, on theend of which are the bevel gear C, D, respectively which mesh with thepinions E, F, mounted on the shafts e, 7, respectively. These shafts arejournaled in the shell or drum G in the interior of which the said fourbevel gears are mounted and which itself forms a part of a sleeve Hloosely surrounding the shafts a, b. The motors A, B, are providedrespectively with-the field magnets J, K, which are connected with theprimary rheostat L, and the secondary rheostat M by suitable wiring ashereinafter explained.

The sleeve H carries a spur gear N from which power is communicated tothe load so that said sleeve may be regarded as the load This sleevealso carries a worm O, which meshes with the worm wheel P on anindependent shaft, and which in turn engages the worm wheel Q, on shaft9 which may be called the secondary rheostat shaft. This shaft carriesthe worm R, which meshes rheostat M and also carries the worm T thepurpose of which will be hereinafter explained.

The wiring of the motors and their fields, with the two rheostats ispreferably as follows:-Main feed wire h, supplies current to the motorsA, B, through the wire j by the aid of suitable brushes in, 7:, and thereturn current passes out through the brushes k through the return wireZ to the main return wire m. The main feed wire it is connected with thearm a of the primary rheostat L through the wire 0. From one end of thisrheostat the wire 72 leads to the field magnet J while from the otherend of the rheostat the wire 79 leads to the field magnet K. The-arm nis moved by hand to the right orleft. As shown the arm is at the centerand therefore the resistance is equally divided between the two fieldcircuits. By turning this arm to the right the resistance is added tothe circuit of field K and out out of field J. Vhen the arm however isturned to the left resistance is added to the circuit of field J and cutout from that of field K. The return wires 9, g from the field magnetsrespectively lead to opposite ends of the secondary rheostat M andthence through the arm 1- to the main return wire m by the wire 8.

The operation of the device, as thus far describe is as follows :'Withthe arm n of the rimary or transmitting rheostat L at the centralposition as shown in the drawing, there will be an equal amount ofresistance in each field. Consequently both fields will be of equalmagnetic strength and the tendency of both motors will be to ro tate'atthe same speed, but in opposite directions. The bevel gear O, D, willthus revolve at equal speed turning the gear E, F, upon their axes butwith no tendency to 1'0- tate the drum G in which they are located.There will therefore be no rotation of the load shaft H. If the arm n ofthe rheostat L is turned to the left it cuts out resistance from thefield magnet K and at the same time adds resistance to field magnet J.This reduces the speed of the armature of motor B and increases that ofmotor A. The difference of speed thus produced between the gears C, D,in favor of 0 produces by well known laws a rotation of the drum G inthe direction determined by the gear C, equal to one half the differencein speed between C and l), and the load is moved accordingly. Ifhowever, the arm n of the rheostat L is turned to the right, themagnetic strength of the magnet J is increased while that of magnet K isdecreased, thus causing the armature of the motor A to lose speed whilethat of motor B gains speed. The difference of speed thus producedbetween the gears C, D, is in favor of D and the rotation of the drum Gand the motion of the load again equals half the difference in speedbetween the two gears but in the opposite direction from that caused byturning the arm of the rheostat to the left. Whenever the load rotates,the arm 7', of the rheostat M, is moved by means of the worm O, wormwheel B, worm gear Q, shaft 9 and worm R in a directlon so related tothe movement of the arm n of rheostat L as to tend to bring the tworesistances back to an equality by cutting in at the secondary rheostatan amount of resistance equal to that cut out at the primary rheostatfor one circuit, and cutting out the amount cut in for the othercircuit. As soon as the two resistances have been made equal again, theload becomes stationary. In addition to this somewhat synchronouscontrol of the two rheostats, it is often dosirable to control thesecondary rheostat and the load directly without usin the primaryrheostat. To accomplish this Thave devised a direct-action control andcut off which I will now describe.

A small motor A, is mounted on the shaft a which carries a worm O whichengages a gear C mounted on the resistance carriage of the rheostat M.Rotation of this motor A in either direction therefore turns theresistance carriage without moving the arm 7" and thus disturbs theelectric balance of the fields J and K resulting in a correspondingrotation of the load-shaft. This rotation returns the arm 7' to itscentral position by moving it to correspond to the displacements of thecarriage. The current to drive the motor A is received from the mainfeed Wire h, through the wire 0, by-

the push-buttons or other switch, 1, 2, 3. The operation of this pushbutton control instead of the primary rheostat control is effectedthrough a novel combined automatic switch and cutoff V which I havedevised for this purpose, and to which the push buttons are connected bysuitable wires t, t and t. One of these buttons directs the current sothat the motor A will move in one direction, the second push buttondirects the current so as to cause the motor A to move in the otherdirection, while the third bush button turns the current back from thecombined switch and cutoff so that the rheostat M is brought back to itsnormal position. The first two push buttons, in cases of ship control,may be called the larboard and starboard push buttons as one will causethe ship to go to port and the other to starboard. This combined switchand cutoff consists essentially of five concentric isolated rings '1),a), v, o, o and two arms to, 'w, sweeping over the rings as turned bythe worm wheel T meshing with the worm T on shaft 9 as before mentioned.The arm 'w connects the two outer rings a, '0 with the next to the innerring Q23, while the other arm to connects the inner ring o with themidle ring 12. It will be noticed that the contact surface of the twoinner rings is continuous and that of the other three rings is broken byinsulating spaces. It will also be noticed that the switch and 'cutoifmay insulating 5 aces of the two outer rings are quite exten edandoverla at their meeting ends. The object of this construction is thatwhen the arm 10' is turned to the ri. ht it connects the inner ring withthat portion of the middle ring which is in electrical connection with alarboard button, while when turned to the left makes such connectionwith that portion of the middle ring which is connected with thestarboard push button. On the other hand, when the arm to is turned soas to sweep over the insulating portions of the outer rings it may cutout either of the rings but is always in position -to be returned by acurrent from the op 0- site push button. The operation of t is pushbutton control through the combined be briefly described as follows:When t e. push button 1 is' pushed, the current flows through wire t,eld u, to the outer ring 1); thence across bar or arm '11; to the innerring segment a thence by the wire 3 to the armature A and through thereturn wire 5 to the main return wire m. As a result of establishlngthis circuit the pilot motor A turns the rheostat M in one direction asfar as desired. Later the electrical balance is restored by theoperation of the shaft 9 as beforedescribed. When however the pushbutton 2, is ushed, the current passes over the wire it t ro segment 1:thence along the bar w to the ring v? wire 3 and armature A tu it in theopposite direction. Should it be desired at an time to return the load,in this case rud er of the ship, to its initial position, the third pushbutton 3 is employed. When this in done a'current; passes through thewire t to the inner Should the ap aratus be in the shown in the '0.position rawing no efiect would be I pzpduced, but as the armsw, 40',must have n shifted somewhat to the right or left according as button 1or button 2 has been used, the arm '10 will be in sition to connect saidring '1) with that ha f of the middle rin '0" which corresponds or isconnected -wi the unused push button. The current is thus automaticallyswitchedto the proper one of. the other buttons to cause it to return tothe midship, ition and is there automatically cut out ivi-the insulatedsection. Another use for t is push button conugh the field u to the'ring trol is to a ply it to the primary rheostat instead of esecondary. All that this requires is to connect the motor A to the armor base of the rheostat L instead of to the rheostat M.

The many uses .and advanta es of this in.- vention will, I think, beread' y understood without further explanation.

I claim: i p

1. An apparatus for controlling electric motors WhlCh consists of anumber of dynamo-electric machines, a rheostat whereby the relativestrength of the field magnets of said machines is varied and controlled,and a pilot motor operating said rheostat;-said rheostat being alsooperated with the load to restore said rheostat to its normal position.

2. An apparatus for controlling electric motors which consists of anumber of dyname-electric machines, a rheostat whereby the relativestrength of the field magnets of said machines is varied and controlled,a

pilot motor operating said rheostat and a' consists of a number ofconcentric insulated rings and a number of arms adapted to pass over thesame, in such manner as to supply current to a suitable pilot motor andcause the sameto rotate in one direction or the other as desired, or tocut off the current automatically at the end of the-stroke andat thecentral position when required and a pilot motor to which said currentis applied.

4. In an apparatus for controlling electric motors, a combined switchand cut-ofi whereby the operation of the driven mechanism is controlled,andwhich consists mainly of a three push button control,-one buttoncausing said driven mechanism to move in one direction, another buttoncausing said mechanism to move in the opposite direction, and

\ the third button acting to restore said mechanism to its centralposition.

HARRY E. DEY.

Witnesses:

Y W. P. Plmnm, Jr.,-

Hanan G. Monrrrr.

